The invention relates to a loading drive system for loading or unloading a disk such as a CD on a disk player.
A loading drive system for a disk driver for CDs, CD-ROMs, and MDs uses a loading motor driven by a loading driver, which is adapted to receive:
a logic control signal for switching the operation of the motor from one mode to another among forward, reverse, and stop modes;
and a reference voltage for setting an output voltage of the loading driver.
FIG. 1 shows such a conventional loading drive system. A controller 11 shown in FIG. 1 has a microcomputer to generate, at the output terminals PC1-PC3 thereof, logic control signals L1 and L2, to generate a forward, a reverse and a stop signals, and a reference voltage signal Vi for setting the output voltages to be supplied to a loading motor. A loading driver 12 receives, at the input terminals PL1-PL3 thereof, the logic control signals L1 and L2, and the reference voltage signal Vi, to generate at the output terminals PL4 and PL5 thereof, drive voltages Vo1 and Vo2 for the loading motor 13, based on the logic control signals L1 and L2 and the reference voltage signal Vi.
In this example, the reference voltage Vi is supplied from the output terminal PC1 of the controller 11 to the input terminal PL1 of the loading driver 12. At the same time, the logic control signals L1 and L2 are supplied from the output terminals PC2 and PC3 of the controller 11 to the input terminals PL2 and PL3 of the loading driver 12. The logic control signals L1 and L2 together define a forward, a reverse, and a stop signal for the loading motor 3, in terms of combinations of their HIGH and LOW levels of the logic control signals, which are for example HIGH-LOW, LOW-HIGH, and LOW-LOW.
The loading driver 12 determines, from the logical status of the logic control signals L1 and L2 and the level of the reference voltage signal Vi, the value and the polarity of the output voltage to be supplied to the loading motor 13 and generates appropriate output voltages Vo1 and Vo2 at the output terminals PL4 and PL5 thereof, based on the value and the polarity. The loading motor 13 is driven by the output voltages Vo1 and Vo2 of the loading driver.
Thus, a conventional loading drive system requires two signal lines for supplying the loading driver 12 with logic control signals L1 and L2 for establishing a forward, a reverse, and a stop mode signal, and another line for supplying a reference voltage signal Vi, hence requiring three lines in total for setting up the output voltage for the motor. The loading drive system also requires a corresponding number of input and output terminals.
It is therefore an object of the invention to provide a loading drive system having a fewer signal lines, and hence a fewer output and input terminals, or pins, for supplying logic control signals along with a reference voltage signal from a controller to a loading driver.
A loading drive system according to the invention comprises:
a control section 21 which converts a given reference voltage signal Vi and a multiplicity of logic control signals (e.g. two logic signals L1 and L2) to a first control voltage Vi1 and a second control voltage Vi2 such that the difference between said first and second control voltages Vi1 and Vi2, respectively, represents said reference voltage Vi and the polarity (including nullity) of said difference represents combinations of said logic control signals;
a loading driver 23 for performing, upon receipt of said first and second control voltage Vi1 and Vi2, respectively, from said control section 21, operations to generate a first output voltage Vo1 by subtracting said second control voltage Vi2 from said first control voltage Vi1 and a second output voltage Vo2 by subtracting said first control voltage Vi1 from said second control voltage Vi2;
said loading drive system outputting said first and second output voltages Vo1 and Vo2, respectively, of said loading driver as the outputs of the loading drive system.
Thus, the invention may reduce not only the number of signal lines required for supplying the loading driver with logic control signals and a reference voltage signal, but also the corresponding number of input and output terminals or pins, thereby adding a further freedom in the design, and hence facilitating easier design, of a loading driver, under a given limitation on the number of pins.
The loading driver may have a muting circuit which converts the first control voltage Vi1 and/or the second control voltage Vi2 received from the control section 21 to zero volt when the first control voltage Vi1 and/or the second control voltage Vi2 are (is) below a predetermined level.
Thus, when the first and/or the second control voltages Vi1 and Vi2, respectively, are (is) lower than the predetermined level, the muting circuit mutes. That is, the muting circuit converts the first and/or the second voltages to zero volt prior to the operations as described above. This enables canceling out the offset voltages in the first and second control voltages Vi1 and Vi2, i.e. output saturation voltages that remain in the first and second control voltages Vi1 and Vi2, thereby improving the input-output characteristics of the loading drive system and the range of control voltages available to the loading driver.
The loading driver is provided with:
first voltage-current conversion means for converting the first control voltage Vi1 received from the control section 21 into a first current I1xe2x80x2;
second voltage-current conversion means for converting the second control voltage Vi2 received from the control section 21 into a second current I2xe2x80x2;
first current-voltage conversion means for converting current I1, which is the first current I1xe2x80x2 minus the second current I2xe2x80x2, into a first voltage; and
second current-voltage conversion means for converting current 12, which is the second current I2xe2x80x2 minus the first current I1xe2x80x2, into a second voltage, to thereby perform the aforementioned operations in terms of the converted currents I1 and I2.
In this arrangement, the aforementioned operations to obtain output voltages Vo1 and Vo2 from the first and the second control voltages Vi1 and Vi2, respectively, received from the control section 21, may be performed easily and correctly.
In another aspect of the invention, a loading drive system comprises:
a control section 21 which converts a reference voltage signal and a multiplicity of logic control signals (e.g. two logic signals L1 and L2) to a first control voltage Vi1 and a second control voltage Vi2 such that the difference between said first and second voltages Vi1 and Vi2, respectively, represents said reference voltage Vi and the polarity (including nullity) of said difference represents combinations of said logic control signals:
a loading driver 23 for performing, upon receipt of said first and second voltages from said control section, operations to generate an output voltage by subtracting said first voltage from said second voltage or by subtracting said second voltage from said first voltage;
said loading drive system outputting said first and second output voltages of said loading driver as the outputs of the loading drive system.
This loading drive system may also incorporate therein muting circuits, voltage-current conversion means and current-voltage conversion means similar to those described above in connection with the preceding example.
Thus, although the level of the drive output voltage is somewhat reduced, the system advantageously has a simple structure in carrying out the aforementioned operations, and a simple output structure requiring a minimum number of output buffers and output terminals.